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March 31, 2000

Christmas Tree Scouting Report

This is the first regular Christmas Tree Scouting Report for the year 2000. The next report will be available after 4 PM on April 7. To receive a FAX of this week’s message, please call (814) 865-1636. 

Many of the early pests are already active in the Harrisburg area, making this season about 2 weeks ahead of 1999. Forsythia has been in full bloom for a week and many different deciduous trees are beginning to leaf out.

The first white pine weevils of the year were captured in detection traps in Perry County on March 14. Eggs were present in the female’s abdomens but we could not find any evidence of feeding on the leaders of the white pine trees in the study area. We continue to collect weevils from the traps but the numbers have decreased. Mike Masiuk, Penn State Extension Agent in Allegheny County, reported signs of adult feeding in Beaver and Westmoreland County. Growers wishing to protect the leaders of their white pine, Douglas fir, and spruce trees should apply a registered insecticide to the top 1/3 of the trees as soon as possible. This early spring weevil activity may make a second application necessary. We will continue to monitor and report activity for the next several weeks.

Balsam twig aphid nymphs have started to feed on the underside of true fir needles at locations in Berks and Schuylkill counties. The minute green nymphs recently hatched from the overwintering eggs and will mature into stem mothers about the time of budbreak. Since these nymphs do not cause any damage, control can safely be delayed to allow for most of the eggs to hatch. But, any attempt at chemical control of balsam twig aphid must be completed before budbreak.

With the blooming of forsythia, it is time to control Cooley and eastern spruce gall adelgids. Forsythia is the traditional plant phenological indicator used successfully used for many years to time sprays against the overwintering nymphs of these two adelgids. On Douglas fir, the black nymphs are beginning to produce white waxy threads to cover themselves. Look for them on the underside of the needles. On Colorado and Norway spruce, the adelgid nymphs are found on the bark at the base of the buds.

Overwintering nymphs of pine bark adelgid have matured on eastern white pine in Berks, Dauphin, Lebanon, Perry, Schuylkill, and Snyder County locations. The females have covered themselves with white waxy threads and have started to lay eggs. Many naturally occurring predators feed on these adelgids and help keep them under control. This adelgid is generally not a serious pest, but may weaken trees already stressed by last year’s drought.

Pales weevils are feeding on the thin bark of eastern white pine twigs in Snyder County. As a result, the branches have started to turn brown. This damage, referred to as flagging, is common when Scotch pine stumps are present. To prevent the damage to standing trees, stumps from trees cut during the last season must be treated. The stump drench technique will also control northern pine weevils, a pest that can cause flagging of healthy trees or kill seedlings and transplants.

Eriophyid mites have hatched from the overwintering eggs and are active on eastern white pine, spruce, and Fraser fir at several locations. These mites are active very early in the season, before the spider mite eggs hatch. They can rapidly build to heavy populations and cause needle silvering or chlorosis. Monitoring population numbers will be useful in making control decisions regarding eriophyid mites.

Now is a good time to finalize pre-season scouting for some persistent pests that will be more difficult to detect after the new growth starts. In Scotch pine twigs, look for striped pine scale or the twig galls caused by pine-pine gall rust. For these pests, culling of infested trees before budbreak is recommended. In all pines, the white, elongate bodies of pine needle scale are easy to detect at this time of the year. Symptoms of rhabdocline needlecast are evident on Douglas fir. Infected trees have distinct red-brown blotches on the needles. On all conifers, the bags from last years’ bagworm are easily detected. Removal of bags containing overwintering eggs will go a long way to keep the population down this year. Taking time to scout now will be worth the effort in May and June.

The next next report will be available after 4 PM on April 7.